Aha, and on what do you base your educated guess?
Anyway, look here. Average playtime according to HowLongToBeat is is 84 hours.
113 * 10 ^ 6 h / 84 h = 1.5 * 10 ^ 6
"Oh noes, EA only sold 1.5 million copies of teh game. Teh world come crashing downs arounds me, bestest RPGs eva no sell good."
Sarcasm aside, I personally think 84 hours is too high for a game with 150+ hours of filler content, my personal educated guess is that the average playtime is somewhere between 40 to 60 hours, but you wanted some evidence and there you have it. Evidence.
Just out of curiosity, this site has the average amount of playtime for DAI, yes? And this is based off a sample size of what? 1000 people if we take the right hand side of the middle graph? 1000 people from the 1 million plus people who bought the game (since we don't know the number, I went off an estimate it for sure hit).
A 0.001% (probably even less) of the people who bought the game is not a representative sample size of all the people who bought the game. Even the ME3 ending polls had more data than this. Also to take into account: what about the casual fanbase, which makes up the majority of people who buy any game? Tell me, who would be more likely to go on the Internet and post their statistics about gameplay time. Would it be the hardcore/invested fans, or would it be the majority (the casuals) who are most likely to either:
1) Buy the game and never play it (we know Steam has done this very well with their sales, at about 37 % the rate at which people never play games. Consoles probably have a smaller percentage, but it's still something not to discount, even if it's 10%
2) Buy the game, play it for a few hours, and then give up/move on to other things
3) Buy the game, play it a little, but focus more on multi-player (you know, for the social experience that they get in games like Call of Duty and sports titles)
I think we might all underestimate just how big of a proportion casual gamers are (graph obtained from Gamasutra here. It's an interesting read
: http://www.gamasutra...al_.php?print=1

As we can see, ultra-casual and casual gamers (i.e: the ones who might buy a game and never play it/very little) make up a massive amount compared to those who are actually invested and who are willing to go on forums, post their playtimes, discuss the game, etc.
If we take your example for the hours played from that site, we can conclude that the people who are posting their times are at least somewhat interested in sharing their experiences, since they spent a good amount of time playing. If we take the 40-60 hour estimate you gathered from the website's data, and we say that about 50% are hardcore fans (reasonable, IMO, for comparison's sake), then here comes some math 
50 hour average play time based on site and your estimate.
50/50 split for site date in terms of casual/hardcore, but the casual gamer's data have much more weight than the hardcore gamer's data, which is what I will attempt to calculate now.
In that case, that 50 hour estimate has to be counterbalanced by the fact that hardcore gamers (the ones who tend to post those kind of stats) make up about 20% of the gamer population (we know that hardcore gamers represent a small fraction of all the gamers out there, so this makes sense IMO, especially if you try to visualize it on the graph)
So, if we split it right up the middle and say that a hardcore gamer has an average 80 hour playthrough, and the average of all casual players is about 20 hours (don't forget those who don't even boot up the game bring down this average)
(80 * 0.2) + (20 * 0.8) = 32 hours
So, an average playthrough including data from the massive casual population vs. the small sample size website you chose , and we get 32 hours, so:
113 000 000 / 32 = 3.5 million copies sold in about 2 and 1/2 months
I don't see any failure there. It took Dragon Age Origins 3 months to hit 3.2 million copies sold, and it took Dragon Age Inquisition 2 and 1/2 months to reach 3.5, not to mention it had to deal with bad publicity from DA2. So for Bioware and EA, I'd say mission accomplished. I can't wait to build myself a new PC and play this game in the summer 